is the unseparated cross section without the phase space factor.
We stress that for both the modulations of \(A_{LL}\)  the longitudinal target polarization is defined relative to the
direction of the virtual photon. In experiments the target polarization is usually defined relative to lepton beam
direction. The transform from one definition to the other one is investigated in great detail in the work by
Diehl and Sapeta [1]}. According to that work, the following relation
\(A_{LL}^{P,l}\,=\,\cos {\theta _\gamma } A_{LL}^{P} - \sin {\theta _\gamma }\,A_{LT}^{P}(\phi _S=0)\) 
